Hydraulic jet stream driller

ABSTRACT

This invention comprises an hydraulic jet stream driller that utilizes a column of drilling mud to supply pressure fluid to three hydraulic drilling jet orifices that are radially spaced from each other within a circle of cutting teeth. The novel tool is preferably clad with galvanized rubber to protect the same from erosion due to the hydraulic and other attrition forces acting on the tool.

United States Patent Mar. 30, 1971 Appl. No. Filed Patented HYDRAULICJET STREAM DRILLER References Cited UNITED STATES PATENTS Hayes Nelsonet al.....

Wells Rowley McKown Primary Examiner.lames A. Leppink Attorney-Ronald W.Mayes 21 Claims, 4 Drawing Figs.

U.S.Cl 175/317, 175/393, 175/422 1nt.Cl ..E2lb41/00, F21c 15/00,F2lb7/18 FieldoiSearch 175/317, 327,422, 393

Patented March 30, 1971 v 3,572,451

a Sheets-Sheet 1.

13 17 79/ 1i 4 79'- [6 w 46' r 4 |l||.-- E v 4s- 65 f 34 as H 51 53 M J2 m, 35' 5 24 2 FIG I INVENTOR. I

BYCONLEY B. COPELAND Patented -March 30, 1971 5 Sheets-Sheet 2 QINVI:'N'I()R.

CONLEY a. COPELAND Patented March 30, 1971 3,512,451

3 Sheets-Sheet 3 CONLEY B. COPELAND HYDRAULIC JET STREAM DRILLERBACKGROUND OF THE INVENTION This invention relates to earth boring. Moreparticularly, this invention relates to an improved drilling bit of thetype having drilling mud jets.

In the rotary method of earth boring customarily used for drilling oilwells, a fluid referred to herein as drilling mud is pumped downwardlythrough a tubular drill string to a drill bit which is connected to thelower end of the drill string. The drilling mud passes through the drillbit and circulates back to the surface through an annular space betweenthe well bore or drill pipe and the drill string, as the drilling mudcirculates it is filtered to remove the debris and cuttings carried fromthe bore hole.

SUMMARY OF THE INVENTION It is an object of this invention to provide anovel fluid-jettype drill bit.

Another object of this invention is the provision of a novelearth-boring-type drilling bit having, in combination, the combinedcutting action of high-pressure hydraulic cutting jets and annularcutting teeth, such as mill teeth.

A further object of this invention is the provision, at the lower end ofa drill string, of an earth-boring-type rotary drilling bit having anannular cutting member with at least one eccentrically locatedhigh-pressure hydraulic cutting jet within the perimeter defined by theannular cutting member to provide a combination cutting action.

Another object of this invention is the provision of a rotary drillingbit, as set forth in the preceding paragraph, adapted to have drillingmud flow down through the drill string, and angularly dispelled throughorifice means formed in an annular wall of the drill bit above theannular cutting member and below other orifice means forming thehydraulic cutting jets, and then recirculating the drilling mud upwardlyin the annular space defined by a clearance between the drill string andthe inner wall of the drill pipe, for carrying cuttings and debrisupwardly therewith.

A still further object of this invention is the provision of a novelfluid-jet-type drill bit having a protective coating or lining of anelastic nonmetallic material, such as vulcanized rubber.

Yet another object of this invention is the provision of a novel rotarydrill bit having a protective coating or lining of an elasticnonmetallic material, such as vulcanized rubber.

In summary, the novel hydraulic jet stream driller, and particularly thenovel rotary drilling bit embodying the invention is provided with arelatively large central opening and annular ball seat thereinpermitting the easy penetration and withdrawal of the drill string intothe drill pipe and/or bore hole free of extraordinarily high compressionon the wall of the bore during entry, and/or the carrying up of mud andslush along with the drill string during withdrawal of the drill string.The mud and slush on the drilling floor forms a dangerous workingenvironment. High compression on the bore wall damages the bore wall andunnecessarily slows the drilling progress. A ball preferably of rubbercoated nylon is adapted to be introduced into the drill string for beingseated on a ball seat of the novel drilling bit prior to theintroduction of the drilling mud. The ball has a density greater thanthat of the drilling mud, but less than that of water or unity so thatthe ball will remain seated when the novel drill bit is put into cuttingoperation. The ball will float up and out of the drill string upon waterbeing introduced into the drill string. Water has a specific gravity ofunity or greater. The term drill pipe as used herein is intended torefer to well casing as distinguished from the drill string. The stringis free to pulled once the ball has been recovered and water is free todrain from the drill string though the novel drill bit into the bore andwell casing.

More particularly, the novel tool, referred to herein as an hydraulicjet stream driller, comprises a section of heavy gauge steel tubingfitted with orifices through which drilling mud is pumped at highvelocity. At the bottom of the tool is a sawtoothlike edge defined bymill teeth of hardened steel. As the tool is turned to the right, themill teeth work in conjunction with the abrasive cutting action of thehigh velocity jet streams of drilling mud to cut up and loosen materialto be circulated out by way of the annular space between the drillstring and the well casing.

One of the special features of this invention is that the tool is linedwith hard rubber that has been bonded to the heavy gauge steel formingthe tool. The rubber lining is preferably of one-sixteenth inchthickness and operates to prevent the tool from wearing out so fast dueto cavitation, abrasion, erosion, and other forces normally encounteredby a. rotary drilling tool.

The invention further resides in certain novel features of construction,combinations, and arrangements of parts and further objects andadvantages of the invention will be apparent to those skilled in the artto which it pertains from the following description of the presentpreferred embodiment thereof described with reference to theaccompanying drawings, which form a part of this specification, whereinthe same reference numerals indicate corresponding parts throughout theseveral views, and in which:

FIG. 1 is a cross-sectional view in elevation of a lower end of atubular drill string having a drilling device attached thereto embodyingthe invention;

FIG. 2 is a cross-sectional-view of the drilling device cmbodying theinvention taken along section line 2-2 of FIG. I;

FIG. 3 is a cross-sectional view of the drilling device embodying theinvention taken along section line 3-3 of FIG. I; and

FIG. 4 is a cross-sectional view of the drilling device embodying theinvention taken along section line 4-4 of FIG. I.

It is to be understood that the invention is not limited to the detailsof construction and arrangements of parts shown in the drawings andhereinafter described in detail, but is capable of being otherwiseembodied and of being practiced and carried out in various ways. It isto be further understood that the terminology employed herein is for thepurpose of description and there is no intention to herein limit theinvention beyond the requirements of the prior art.

Referring to FIGS. 1, 2, 3, and 4, the reference numeral I0 indicatesgenerally a fluid jet cutting device embodying the invention. The device10 is affixed, preferably by welding by a circular bead II, to a lowerend of a tubular drill string 12 within a well casing or drill pipe 13.The well casing 13 has an inner wall that defines a well bore I4 forpurposes of describing and claiming the apparatus of this invention.

More particularly, the device 10 comprises a tubular body I5 having acylindrical body portion 16 and a frustoconical gooseneck portion 17welded by the head 11 at a circular upper end thereof to a circularlower end 19 of the tubular drill string I2. The height of the gooseneckportion I7 is about the same as the height of the cylindrical bodyportion 16 down to an horizontal partition 20. Below the partition 20 isa skirt portion 21 integrally connected to' and depending from thecylindrical body portion I6. 1

The dependent skirt portion 21 is counterbored to have a greaterinternal diameter than the internal diameter of the cylindrical bodyportion 16. The outer diameters of each of the portions 16 and 21 arepreferably the same. At a lower circular end face 22 of the dependingskirt portion 21 is affixed, preferably by a circular weld bead 23, aset of circularly arranged mill teeth 24. The mill teeth 24 are shown inFIGS. I and 2, and define a circular mill cutter, indicated generally bythe reference numeral 25.

The partition 20 is preferably located at the lower end of thecylindrical body portion 16. The skirt portion 21 is of about the sameheight as the cylindrical body portion I6.

Fluid such as liquids including water and drilling mud are channeleddown the tubular drill string I2 into the device It), and moreparticularly into the gooseneck portion 17 and the cylindrical bodyportion 16, through a central bypass passageway 30, and/or a pluralityof fluid jet orifices 31, 32, and 33, centrally formed in threehexagonal head stud bolts 34, 35, and 36, respectively. The stud bolts34, 35, and 36 are threaded into the partition 20 and are equiangularlyspaced from each other in increments of 120. Moreover, as seen in FIGS.2 and 3, the passageway 30 is cylindrically shaped and centrallylocated. The nozzles 31, 32, and 33 are each cylindrically shaped, butare eccentrically located relative to the central passageway 30. Thenozzles 31, 32, and 33 are each located at a different radial distancefrom the central passageway 30 for defining three discrete cutting pathswhen the device is in operation. Preferably, the nozzle 31 is spacedradially inwardly from the nozzle 33 by the same distance that thenozzle 32 is spaced radially outwardly from the nozzle 33.

Fluid from the fluid jet orifices 31, 32, and 33 accumulates within theskirt portion 21 duringthe cutting operation; During the cuttingoperation the entire device 10 is being rotated via the drill string 12in a counterclockwise direction as seen in FIGS. 2 and 3, and in aclockwise direction as seen in FIG. 4. Thusthe circular mill cutting 25is put into effective use. The fluid jet orifices 31, 32, and 33 willnot be effective as cutting means, however, unless a rubber coated nylonball 40, having a density greater than that of the drilling fluid or mudand less than that of water or unity, is seated on a ball seat 41. Theball seat 41 is cylindrically shaped and is press fitted into acounterbore 42 of the passageway 30.

The passageway 30 is centrally fonned in a tubular ball seat portion 44of the partition 20. The ball seat portion 44 extends above an annularplanar portion 45 of the partition into which the stud bolts 34, 35, and36 are threaded. The upper end of the ball seat portion 44 iscountersunk to form a funnelshaped or outwardly flared upper end portion46 of the passageway 30. The portion 46 serves as a guide for the ball40 onto its seat 42. The ball seat 42 has a sharp circular inner edge 47that provides line contact with the rubber coating of the ball 40 foreffectively partitioning and thereby isolating the passageway 30 fromthe upper side of the partition 20 and prevents the transgression offluid therepast.

The buildup of fluid, cuttings, and other debris beneath the partition20 is released through preferably four cylindrical peripheral ports 51,52, 53, and 54 formed in the skirt 21, FIGS. 1 and 3.

In order to obtain the maximum benefit of the fluid buildup within thecylindrical inner chamber defined by the skirt 21, as seen in FIGS. 1and 3, the four ports 51, 52, 53, and 54 are drilled at a tangent to acircle concentric within the skirt 21, but having a diameter less thanthat of the skirt 21 and greater than the diameter of the ball 40, andtherefore may be described as having been drilled along a chord of acircle. The ports 51, 52, 53, and 54 are not radial and are nottangential to the skirt 21. The ports 51, 52, 53, and 54 are located ina plane about one-third of the distance from the partition 20 to thecutting edges of the mill teeth 25. Once the spent fluid, cuttings, andother debris exit the ports 51, 52, 53, and 54, the fluid is forcedupwardly through an annular space between the outer surface of thedevice 10 and the well bore 14, and then subsequently between the drillstring 12 and the well bore 14, to the surface where the fluid ispreferably filtered, and recirculated down through the drill string 12and into the device 10.

A novel feature of this invention is the provision of the nonmetallicelastic lining or coating of the exterior 60 of the device 10 and thewalls or surfaces 62 and 63 of the chamber within the skirt 21 of thedevice 10. The lining is preferably of a vulcanized hard rubber bondedto the heavy gauge steel body 15 and is indicated generally by thereference numeral 70. Preferably, the ports 51, 52, 53, and 54 are alsolined with vulcanized rubber. The object of the rubber lining 70 is toprotect the portions of the device 10 that are exposed to the highlyturbulent and erosive hydraulic cutting action of the fluid jettingthrough the nozzles 31, 32, and 33, as well as the abrasive action ofthe cuttings and other debris. The rubber vention such modifications asmay be considered to fall within the scope of the appended claimslclaim:

1. in an apparatus adapted to be lowered in a well bore on a tubularstring, fluid jet cutting means having drill bit means comprisingcircular mill cutter means adapted to rotate about a central axis forperforming a cutting action in a bottom of a well bore, fluid jetpassage means comprising horizontal partition means with orifice meansformed therein eccentrically of said central axis and adapted to directjet streams of drilling fluid in a downward direction parallel to saidcentral axis, relatively large closable central cylindrical openingmeans coaxial with said central axis in said partition means forpermitting fluid to pass therethrough when introducing and removing saidjet cutting means from the well bore, tubular skirt means depending fromsaid partition means and having said circular mill cutter meansconnected thereto at a downwardly facing edge thereof, means formingrelatively large openings in said tubular skirt means for directingfluid horizontally outwardly thereof at a 45 included angle with adiameter of said skirt means against the wall of the well bore in such amanner that the fluid is permitted to flow downwardly in the tubularstring and through said orifice means and into said tubular skirt meansand against a bottom of the well bore and through said relatively largeopening means against the wall of the well bore for carrying cuttingsand other debris upwardly between the tubular string and the well bore,a rubber-coated nylon ball having density less than that of water andgreater than that of drilling mud, and a seat for said ball formed inthe upper end of said cylindrical opening means for seating said ballthereon and closing said central cylindrical opening means when drillingmud has been introduced into the tubular string and for opening the sameby introducing water into the tubular string and floating said ball offsaid seat and recovering said ball at the upper end of the tubularstring.

2. ln an apparatus as set forth in claim 1, wherein said orifice meansformed in said partition means comprise three orifices equiangularlydisplaced each other and radially spaced from each other in such amanner as to define three discrete cutting paths.

3. In an apparatus as set forth in claim 1, elastic nonmetallic meansbonded to and lining said tubular skirt means and a lower side of saidpartition means.

4. In an apparatus as set forth in claim 3, wherein said elasticnonmetallic means is vulcanized rubber.

5. In an apparatus adapted to be lowered in a well bore on a tubularstring, fluid jet cutting means having drill bit means comprisingcircular mill cutter means adapted to rotate about a central axis forperforming a cutting action in a bottom of the well bore, fluid jetpassage means comprising transverse partition means with orifice meansformed therein eccentrically of said central axis and adapted to directjet streams of drilling fluid in a downward direction parallel to saidcentral axis, relatively large closable central cylindrical openingmeans coaxial with said central axis formed in said partition means forpermitting fluid to pass therethrough when introducing and removing saidjet cutting means from the well bore, tubular skirt means depending fromsaid partition means and having said circular mill cutter meansconnected thereto at a downwardly facing edge thereof, means formingrelatively large openings in said tubular skirt for directing fluidoutwardly thereof against the wall of the well bore in such a mannerthat the fluid is permitted to flow downwardly in the tubular string andthrough said orifice means and into said tubular skirt means and againsta bottom of the well bore and through said relatively large openingmeans against the wall of the well bore for carrying cuttings and otherdebris upwardly between the tubular string and the well bore, a ballhaving a density of less than that of water and greater than that ofdrilling mud, and a seat for said ball formed in the upper end of saidcentral cylindrical opening means for seating said ball thereon andclosing said central cylindrical opening means when drilling mud hasbeen introduced into the tubular string and for opening the same byintroducing water into the tubular string and floating said ball offsaid ball seat and recovering the same at the upper end of the tubularstring.

6. In an apparatus as set forth in claim 5, wherein said orifice meansformed in said partition means define a plurality of discrete cuttingpaths.

7. in an apparatus as set forth in claim 5, elastic nonmetallic meanslining said tubular skirt means and a lower side of said partitionmeans. Y

8. In an apparatus adapted to be lowered in a well bore on a tubularstring, fluid jet cutting means having drill bit means comprising cuttermeans adapted to rotate about a central axis for performing a cuttingaction in a bottom of the well bore, fluid jet passage means comprisingpartition means with orifice means formed therein eccentrically of saidcentral axis and adapted to direct at least one jet stream of drillingfluid in a downward direction, relatively large closable centralcylindrical opening means coaxial with said central axis formed in saidpartition means for permitting fluid to pass therethrough whenintroducing and removing said jet cutting means from the well bore,tubular skirt means depending from said partition means and having saidcutter means connected thereto, means forming relatively large openingsin said tubular skirt for directing fluid outwardly thereof against thewall of the well bore in such a manner that the fluid is permitted toflow downwardly in the tubular string and through said orifice means andinto said tubular skirt means and against a bottom of the well bore andthrough said relatively large opening means against the wall of the wellbore for carrying cuttings and other debris upwardly between the tubularstring and the well bore, a ball having a'density of less than unity andgreater than that of the drilling fluid, and a seat for said ball formedin the upper end of said central cylindrical opening means for seatingsaid ball thereon and closing said central cylindrical opening meanswhen a fluid of a density less than the density of said ball has beenintroduced into the tubular string and for opening the same byintroducing fluid of a density greater than the density of said ballinto the tubular string and floating said ball off said ball seat andrecovering the ball at the upper end of the tubular string.

' 9. In an apparatus as set forth in claim 8, wherein said cutter meanscomprise a circle of mill cutter teeth affixed to a downwardly facingedge of said tubular skirt means.

10. In an apparatus as set forth in claim 8, elastic nonmetalhe meanslining said tubular skirt means.

ll. In an apparatus adapted to be lowered on a tubular string into awell bore, a fluid jetting device including a drill bit having cuttingmeans thereon and jetting nozzle means for performing cutting action ina well bore, said device having a cutting means and below said jettingnozzle means for directing fluid from said port means against a wall ofthe well bore. and said jetting nozzle means adapted to direct cuttingfluid in a downward direction in the well bore.

l2. ln an apparatus as set forth in claim 11, wherein said port meansdirect the fluid at an horizontal vector angle that includes anhorizontal radial vector and an horizontal tangential vector of the wellbore.

13. In an apparatus as set forth in claim 11, wherein said port meansdirect the fluid horizontally outwardly of said fluid jetting device atan acute angle with a diameter of the well bore.

14. In an apparatus as set forth in claim 11, wherein said jettingnozzle means comprise a plurality of axially directed orifices angularlydisplaced from each other. I

15. In an apparatus as set forth in claim 11, wherein said jettingaxially directed nozzle means comprise a plurality of nozzles radiallyspaced from each other in such a manner as to define three discretecuttings paths as said fluid jetting device is rotated.

16. In an apparatus as set forth in claim ll, wherein said drill bitcomprises circularly arranged mill teeth.

17. A drill bit for attachment to a lower end of a tubular drill stringthrough which drilling mud is pumped downwardly to the bit for cleaninga well bore,'the drill bit comprising, in

combination, a drill bit having a body, at least one fluid jet nozzlethrough said body for directing a jet of drilling mud from the body, afluid bypass passageway through said body for passing drilling mudthrough said body, a valve seat in said bypass passageway adapted tohave a valve member seat thereon and block the downward passage ofdrilling mud fluid passage adapted to receive fluid from the tubularstring and including generally radial port means above said drill bit Ithrough said bypass passageway, and port means formed in said body belowsaid fluid jet nozzle for directing the drilling mud laterally outwardlyof said body at an acute angle with a diameter of the well bore.

18. A drill bit as set forth in claim 17, further comprising, incombination, circularly arranged mill teeth affixed to a lower end ofsaid body below said port means.

19. A drill bit as set forth in claim 17, further comprising, incombination, elastic nonmetallic means lining said body at the lower endthereof to protect the same from the hydraulic cutting action of thedrill bit.

20. In an apparatus adapted to be lowered on a tubular string into awell bore, a fluid jetting device including a drill bit having cuttingmeans thereon and jetting nozzle means for performing cutting action ina well bore, and elastic nonmetallic means lining said fluid jettingdevice at the lower end thereof to protect the same from the hydrauliccutting action of the drill bit.

2!. A drill bit attachment to a lower end of a tubular drill stringthrough which drilling mud is pumped downwardly to the bit for cleaninga well bore, the drill bit comprising, in combination, a drill bithaving a body, at least one fluid jet nozzle through said body fordirecting a jet of drilling mud from the body, and elastic nonmetallicmeans lining said body at the lower end thereof to protect the same fromthe hydraulic cutting action of the drill bit.

1. In an apparatus adapted to be lowered in a well bore on a tubularstring, fluid jet cutting means having drill bit means comprisingcircular mill cutter means adapted to rotate about a central axis forperforming a cutting action in a bottom of a well bore, fluid jetpassage means comprising horizontal partition means with orifice meansformed therein eccentrically of said central axis and adapted to directjet streams of drilling fluid in a downward direction parallel to saidcentral axis, relatively large closable central cylindrical openingmeans coaxial with said central axis in said partition means forpermitting fluid to pass therethrough when introducing and removing saidjet cutting means from the well bore, tubular skirt means depending fromsaid partition means and having said circular mill cutter meansconnected thereto at a downwardly facing edge thereof, means formingrelatively large openings in said tubular skirt means for directingfluid horizontally outwardly thereof at a 45* included angle with adiameter of said skirt means against the wall of the well bore in such amanner that the fluid is permitted to flow downwardly in the tubularstring and through said orifice means and into said tubular skirt meansand against a bottom of the well bore and through said relatively largeopening means against the wall of the well bore for carrying cuttingsand other debris upwardly between the tubular string and the well bore,a rubber-coated nylon ball having density less than that of water andgreater than that of drilling mud, and a seat for said ball formed inthe upper end of said cylindrical opening means for seating said ballthereon and closing said central cylindrical opening means when drillingmud has been introduced into the tubular string and for opening the sameby introducing water into the tubular string and floating said ball offsaid seat and recovering said ball at the upper end of the tubularstring.
 2. In an apparatus as set fortH in claim 1, wherein said orificemeans formed in said partition means comprise three orificesequiangularly displaced each other and radially spaced from each otherin such a manner as to define three discrete cutting paths.
 3. In anapparatus as set forth in claim 1, elastic nonmetallic means bonded toand lining said tubular skirt means and a lower side of said partitionmeans.
 4. In an apparatus as set forth in claim 3, wherein said elasticnonmetallic means is vulcanized rubber.
 5. In an apparatus adapted to belowered in a well bore on a tubular string, fluid jet cutting meanshaving drill bit means comprising circular mill cutter means adapted torotate about a central axis for performing a cutting action in a bottomof the well bore, fluid jet passage means comprising transversepartition means with orifice means formed therein eccentrically of saidcentral axis and adapted to direct jet streams of drilling fluid in adownward direction parallel to said central axis, relatively largeclosable central cylindrical opening means coaxial with said centralaxis formed in said partition means for permitting fluid to passtherethrough when introducing and removing said jet cutting means fromthe well bore, tubular skirt means depending from said partition meansand having said circular mill cutter means connected thereto at adownwardly facing edge thereof, means forming relatively large openingsin said tubular skirt for directing fluid outwardly thereof against thewall of the well bore in such a manner that the fluid is permitted toflow downwardly in the tubular string and through said orifice means andinto said tubular skirt means and against a bottom of the well bore andthrough said relatively large opening means against the wall of the wellbore for carrying cuttings and other debris upwardly between the tubularstring and the well bore, a ball having a density of less than that ofwater and greater than that of drilling mud, and a seat for said ballformed in the upper end of said central cylindrical opening means forseating said ball thereon and closing said central cylindrical openingmeans when drilling mud has been introduced into the tubular string andfor opening the same by introducing water into the tubular string andfloating said ball off said ball seat and recovering the same at theupper end of the tubular string.
 6. In an apparatus as set forth inclaim 5, wherein said orifice means formed in said partition meansdefine a plurality of discrete cutting paths.
 7. In an apparatus as setforth in claim 5, elastic nonmetallic means lining said tubular skirtmeans and a lower side of said partition means.
 8. In an apparatusadapted to be lowered in a well bore on a tubular string, fluid jetcutting means having drill bit means comprising cutter means adapted torotate about a central axis for performing a cutting action in a bottomof the well bore, fluid jet passage means comprising partition meanswith orifice means formed therein eccentrically of said central axis andadapted to direct at least one jet stream of drilling fluid in adownward direction, relatively large closable central cylindricalopening means coaxial with said central axis formed in said partitionmeans for permitting fluid to pass therethrough when introducing andremoving said jet cutting means from the well bore, tubular skirt meansdepending from said partition means and having said cutter meansconnected thereto, means forming relatively large openings in saidtubular skirt for directing fluid outwardly thereof against the wall ofthe well bore in such a manner that the fluid is permitted to flowdownwardly in the tubular string and through said orifice means and intosaid tubular skirt means and against a bottom of the well bore andthrough said relatively large opening means against the wall of the wellbore for carrying cuttings and other debris upwardly between the tubularstring and the well bore, a ball having a density of less than unity andgreater than That of the drilling fluid, and a seat for said ball formedin the upper end of said central cylindrical opening means for seatingsaid ball thereon and closing said central cylindrical opening meanswhen a fluid of a density less than the density of said ball has beenintroduced into the tubular string and for opening the same byintroducing fluid of a density greater than the density of said ballinto the tubular string and floating said ball off said ball seat andrecovering the ball at the upper end of the tubular string.
 9. In anapparatus as set forth in claim 8, wherein said cutter means comprise acircle of mill cutter teeth affixed to a downwardly facing edge of saidtubular skirt means.
 10. In an apparatus as set forth in claim 8,elastic nonmetallic means lining said tubular skirt means.
 11. In anapparatus adapted to be lowered on a tubular string into a well bore, afluid jetting device including a drill bit having cutting means thereonand jetting nozzle means for performing cutting action in a well bore,said device having a fluid passage adapted to receive fluid from thetubular string and including generally radial port means above saiddrill bit cutting means and below said jetting nozzle means fordirecting fluid from said port means against a wall of the well bore,and said jetting nozzle means adapted to direct cutting fluid in adownward direction in the well bore.
 12. In an apparatus as set forth inclaim 11, wherein said port means direct the fluid at an horizontalvector angle that includes an horizontal radial vector and an horizontaltangential vector of the well bore.
 13. In an apparatus as set forth inclaim 11, wherein said port means direct the fluid horizontallyoutwardly of said fluid jetting device at an acute angle with a diameterof the well bore.
 14. In an apparatus as set forth in claim 11, whereinsaid jetting nozzle means comprise a plurality of axially directedorifices angularly displaced from each other.
 15. In an apparatus as setforth in claim 11, wherein said jetting axially directed nozzle meanscomprise a plurality of nozzles radially spaced from each other in sucha manner as to define three discrete cuttings paths as said fluidjetting device is rotated.
 16. In an apparatus as set forth in claim 11,wherein said drill bit comprises circularly arranged mill teeth.
 17. Adrill bit for attachment to a lower end of a tubular drill stringthrough which drilling mud is pumped downwardly to the bit for cleaninga well bore, the drill bit comprising, in combination, a drill bithaving a body, at least one fluid jet nozzle through said body fordirecting a jet of drilling mud from the body, a fluid bypass passagewaythrough said body for passing drilling mud through said body, a valveseat in said bypass passageway adapted to have a valve member seatthereon and block the downward passage of drilling mud through saidbypass passageway, and port means formed in said body below said fluidjet nozzle for directing the drilling mud laterally outwardly of saidbody at an acute angle with a diameter of the well bore.
 18. A drill bitas set forth in claim 17, further comprising, in combination, circularlyarranged mill teeth affixed to a lower end of said body below said portmeans.
 19. A drill bit as set forth in claim 17, further comprising, incombination, elastic nonmetallic means lining said body at the lower endthereof to protect the same from the hydraulic cutting action of thedrill bit.
 20. In an apparatus adapted to be lowered on a tubular stringinto a well bore, a fluid jetting device including a drill bit havingcutting means thereon and jetting nozzle means for performing cuttingaction in a well bore, and elastic nonmetallic means lining said fluidjetting device at the lower end thereof to protect the same from thehydraulic cutting action of the drill bit.
 21. A drill bit attachment toa lower end of a tubular drill string through which drilling mud ispumped downwardly to the bIt for cleaning a well bore, the drill bitcomprising, in combination, a drill bit having a body, at least onefluid jet nozzle through said body for directing a jet of drilling mudfrom the body, and elastic nonmetallic means lining said body at thelower end thereof to protect the same from the hydraulic cutting actionof the drill bit.